[PATCH v10 0/2] Improved Memory Tier Creation for CPUless NUMA Nodes

[PATCH v10 0/2] Improved Memory Tier Creation for CPUless NUMA Nodes

[Ho-Ren (Jack) Chuang]

When a memory device, such as CXL1.1 type3 memory, is emulated as
normal memory (E820_TYPE_RAM), the memory device is indistinguishable from
normal DRAM in terms of memory tiering with the current implementation.
The current memory tiering assigns all detected normal memory nodes to
the same DRAM tier. This results in normal memory devices with different
attributions being unable to be assigned to the correct memory tier,
leading to the inability to migrate pages between different
types of memory.
https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/

This patchset automatically resolves the issues. It delays the
initialization of memory tiers for CPUless NUMA nodes until they obtain
HMAT information and after all devices are initialized at boot time,
eliminating the need for user intervention. If no HMAT is specified,
it falls back to using `default_dram_type`.

Example usecase:
We have CXL memory on the host, and we create VMs with a new system memory
device backed by host CXL memory. We inject CXL memory performance
attributes through QEMU, and the guest now sees memory nodes with
performance attributes in HMAT. With this change, we enable the
guest kernel to construct the correct memory tiering for the memory nodes.

- v10:
 Thanks to Andrew's and SeongJae's comments,
 * Address kunit compilation errors
 * Resolve the bug of not returning the correct error code in
   `mt_perf_to_adistance`
-v9:
 * Address corner cases in `memory_tier_late_init`. Thank Ying's comments.
 * https://lore.kernel.org/lkml/20240329053353.309557-1-horenchuang@bytedance.com/T/#u
-v8:
 * Fix email format
 * https://lore.kernel.org/lkml/20240329004815.195476-1-horenchuang@bytedance.com/T/#u
-v7:
 * Add Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
-v6:
 Thanks to Ying's comments,
 * Move `default_dram_perf_lock` to the function's beginning for clarity
 * Fix double unlocking at v5
 * https://lore.kernel.org/lkml/20240327072729.3381685-1-horenchuang@bytedance.com/T/#u
-v5:
 Thanks to Ying's comments,
 * Add comments about what is protected by `default_dram_perf_lock`
 * Fix an uninitialized pointer mtype
 * Slightly shorten the time holding `default_dram_perf_lock`
 * Fix a deadlock bug in `mt_perf_to_adistance`
 * https://lore.kernel.org/lkml/20240327041646.3258110-1-horenchuang@bytedance.com/T/#u
-v4:
 Thanks to Ying's comments,
 * Remove redundant code
 * Reorganize patches accordingly
 * https://lore.kernel.org/lkml/20240322070356.315922-1-horenchuang@bytedance.com/T/#u
-v3:
 Thanks to Ying's comments,
 * Make the newly added code independent of HMAT
 * Upgrade set_node_memory_tier to support more cases
 * Put all non-driver-initialized memory types into default_memory_types
   instead of using hmat_memory_types
 * find_alloc_memory_type -> mt_find_alloc_memory_type
 * https://lore.kernel.org/lkml/20240320061041.3246828-1-horenchuang@bytedance.com/T/#u
-v2:
 Thanks to Ying's comments,
 * Rewrite cover letter & patch description
 * Rename functions, don't use _hmat
 * Abstract common functions into find_alloc_memory_type()
 * Use the expected way to use set_node_memory_tier instead of modifying it
 * https://lore.kernel.org/lkml/20240312061729.1997111-1-horenchuang@bytedance.com/T/#u
-v1:
 * https://lore.kernel.org/lkml/20240301082248.3456086-1-horenchuang@bytedance.com/T/#u

Ho-Ren (Jack) Chuang (2):
  memory tier: dax/kmem: introduce an abstract layer for finding,
    allocating, and putting memory types
  memory tier: create CPUless memory tiers after obtaining HMAT info

 drivers/dax/kmem.c           |  20 +-----
 include/linux/memory-tiers.h |  14 ++++
 mm/memory-tiers.c            | 127 ++++++++++++++++++++++++++++++-----
 3 files changed, 126 insertions(+), 35 deletions(-)

-- 
Ho-Ren (Jack) Chuang

[PATCH v10 1/2] memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

[Ho-Ren (Jack) Chuang]

Since different memory devices require finding, allocating, and putting
memory types, these common steps are abstracted in this patch,
enhancing the scalability and conciseness of the code.

Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
---
 drivers/dax/kmem.c           | 20 ++------------------
 include/linux/memory-tiers.h | 13 +++++++++++++
 mm/memory-tiers.c            | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 18 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 42ee360cf4e3..01399e5b53b2 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -55,21 +55,10 @@ static LIST_HEAD(kmem_memory_types);
 
 static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
 {
-	bool found = false;
 	struct memory_dev_type *mtype;
 
 	mutex_lock(&kmem_memory_type_lock);
-	list_for_each_entry(mtype, &kmem_memory_types, list) {
-		if (mtype->adistance == adist) {
-			found = true;
-			break;
-		}
-	}
-	if (!found) {
-		mtype = alloc_memory_type(adist);
-		if (!IS_ERR(mtype))
-			list_add(&mtype->list, &kmem_memory_types);
-	}
+	mtype = mt_find_alloc_memory_type(adist, &kmem_memory_types);
 	mutex_unlock(&kmem_memory_type_lock);
 
 	return mtype;
@@ -77,13 +66,8 @@ static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
 
 static void kmem_put_memory_types(void)
 {
-	struct memory_dev_type *mtype, *mtn;
-
 	mutex_lock(&kmem_memory_type_lock);
-	list_for_each_entry_safe(mtype, mtn, &kmem_memory_types, list) {
-		list_del(&mtype->list);
-		put_memory_type(mtype);
-	}
+	mt_put_memory_types(&kmem_memory_types);
 	mutex_unlock(&kmem_memory_type_lock);
 }
 
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 69e781900082..a44c03c2ba3a 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -48,6 +48,9 @@ int mt_calc_adistance(int node, int *adist);
 int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
 			     const char *source);
 int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
+struct memory_dev_type *mt_find_alloc_memory_type(int adist,
+							struct list_head *memory_types);
+void mt_put_memory_types(struct list_head *memory_types);
 #ifdef CONFIG_MIGRATION
 int next_demotion_node(int node);
 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -136,5 +139,15 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
 {
 	return -EIO;
 }
+
+struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+{
+	return NULL;
+}
+
+void mt_put_memory_types(struct list_head *memory_types)
+{
+
+}
 #endif	/* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 0537664620e5..974af10cfdd8 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -623,6 +623,38 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
 }
 EXPORT_SYMBOL_GPL(clear_node_memory_type);
 
+struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+{
+	bool found = false;
+	struct memory_dev_type *mtype;
+
+	list_for_each_entry(mtype, memory_types, list) {
+		if (mtype->adistance == adist) {
+			found = true;
+			break;
+		}
+	}
+	if (!found) {
+		mtype = alloc_memory_type(adist);
+		if (!IS_ERR(mtype))
+			list_add(&mtype->list, memory_types);
+	}
+
+	return mtype;
+}
+EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
+
+void mt_put_memory_types(struct list_head *memory_types)
+{
+	struct memory_dev_type *mtype, *mtn;
+
+	list_for_each_entry_safe(mtype, mtn, memory_types, list) {
+		list_del(&mtype->list);
+		put_memory_type(mtype);
+	}
+}
+EXPORT_SYMBOL_GPL(mt_put_memory_types);
+
 static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
 {
 	pr_info(
-- 
Ho-Ren (Jack) Chuang

[PATCH v10 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

[Ho-Ren (Jack) Chuang]

The current implementation treats emulated memory devices, such as
CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
(E820_TYPE_RAM). However, these emulated devices have different
characteristics than traditional DRAM, making it important to
distinguish them. Thus, we modify the tiered memory initialization process
to introduce a delay specifically for CPUless NUMA nodes. This delay
ensures that the memory tier initialization for these nodes is deferred
until HMAT information is obtained during the boot process. Finally,
demotion tables are recalculated at the end.

* late_initcall(memory_tier_late_init);
Some device drivers may have initialized memory tiers between
`memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
online memory nodes and configuring memory tiers. They should be excluded
in the late init.

* Handle cases where there is no HMAT when creating memory tiers
There is a scenario where a CPUless node does not provide HMAT information.
If no HMAT is specified, it falls back to using the default DRAM tier.

* Introduce another new lock `default_dram_perf_lock` for adist calculation
In the current implementation, iterating through CPUlist nodes requires
holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
trying to acquire the same lock, leading to a potential deadlock.
Therefore, we propose introducing a standalone `default_dram_perf_lock` to
protect `default_dram_perf_*`. This approach not only avoids deadlock
but also prevents holding a large lock simultaneously.

* Upgrade `set_node_memory_tier` to support additional cases, including
  default DRAM, late CPUless, and hot-plugged initializations.
To cover hot-plugged memory nodes, `mt_calc_adistance()` and
`mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
handle cases where memtype is not initialized and where HMAT information is
available.

* Introduce `default_memory_types` for those memory types that are not
  initialized by device drivers.
Because late initialized memory and default DRAM memory need to be managed,
a default memory type is created for storing all memory types that are
not initialized by device drivers and as a fallback.

Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
---
 include/linux/memory-tiers.h |  5 +-
 mm/memory-tiers.c            | 95 +++++++++++++++++++++++++++++-------
 2 files changed, 81 insertions(+), 19 deletions(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index a44c03c2ba3a..16769552a338 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -140,12 +140,13 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
 	return -EIO;
 }
 
-struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
+					struct list_head *memory_types)
 {
 	return NULL;
 }
 
-void mt_put_memory_types(struct list_head *memory_types)
+static inline void mt_put_memory_types(struct list_head *memory_types)
 {
 
 }
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 974af10cfdd8..44fa10980d37 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -36,6 +36,11 @@ struct node_memory_type_map {
 
 static DEFINE_MUTEX(memory_tier_lock);
 static LIST_HEAD(memory_tiers);
+/*
+ * The list is used to store all memory types that are not created
+ * by a device driver.
+ */
+static LIST_HEAD(default_memory_types);
 static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
 struct memory_dev_type *default_dram_type;
 
@@ -108,6 +113,8 @@ static struct demotion_nodes *node_demotion __read_mostly;
 
 static BLOCKING_NOTIFIER_HEAD(mt_adistance_algorithms);
 
+/* The lock is used to protect `default_dram_perf*` info and nid. */
+static DEFINE_MUTEX(default_dram_perf_lock);
 static bool default_dram_perf_error;
 static struct access_coordinate default_dram_perf;
 static int default_dram_perf_ref_nid = NUMA_NO_NODE;
@@ -505,7 +512,8 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
 static struct memory_tier *set_node_memory_tier(int node)
 {
 	struct memory_tier *memtier;
-	struct memory_dev_type *memtype;
+	struct memory_dev_type *mtype = default_dram_type;
+	int adist = MEMTIER_ADISTANCE_DRAM;
 	pg_data_t *pgdat = NODE_DATA(node);
 
 
@@ -514,11 +522,20 @@ static struct memory_tier *set_node_memory_tier(int node)
 	if (!node_state(node, N_MEMORY))
 		return ERR_PTR(-EINVAL);
 
-	__init_node_memory_type(node, default_dram_type);
+	mt_calc_adistance(node, &adist);
+	if (node_memory_types[node].memtype == NULL) {
+		mtype = mt_find_alloc_memory_type(adist, &default_memory_types);
+		if (IS_ERR(mtype)) {
+			mtype = default_dram_type;
+			pr_info("Failed to allocate a memory type. Fall back.\n");
+		}
+	}
+
+	__init_node_memory_type(node, mtype);
 
-	memtype = node_memory_types[node].memtype;
-	node_set(node, memtype->nodes);
-	memtier = find_create_memory_tier(memtype);
+	mtype = node_memory_types[node].memtype;
+	node_set(node, mtype->nodes);
+	memtier = find_create_memory_tier(mtype);
 	if (!IS_ERR(memtier))
 		rcu_assign_pointer(pgdat->memtier, memtier);
 	return memtier;
@@ -655,6 +672,33 @@ void mt_put_memory_types(struct list_head *memory_types)
 }
 EXPORT_SYMBOL_GPL(mt_put_memory_types);
 
+/*
+ * This is invoked via `late_initcall()` to initialize memory tiers for
+ * CPU-less memory nodes after driver initialization, which is
+ * expected to provide `adistance` algorithms.
+ */
+static int __init memory_tier_late_init(void)
+{
+	int nid;
+
+	mutex_lock(&memory_tier_lock);
+	for_each_node_state(nid, N_MEMORY)
+		if (node_memory_types[nid].memtype == NULL)
+			/*
+			 * Some device drivers may have initialized memory tiers
+			 * between `memory_tier_init()` and `memory_tier_late_init()`,
+			 * potentially bringing online memory nodes and
+			 * configuring memory tiers. Exclude them here.
+			 */
+			set_node_memory_tier(nid);
+
+	establish_demotion_targets();
+	mutex_unlock(&memory_tier_lock);
+
+	return 0;
+}
+late_initcall(memory_tier_late_init);
+
 static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
 {
 	pr_info(
@@ -668,7 +712,7 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
 {
 	int rc = 0;
 
-	mutex_lock(&memory_tier_lock);
+	mutex_lock(&default_dram_perf_lock);
 	if (default_dram_perf_error) {
 		rc = -EIO;
 		goto out;
@@ -716,23 +760,30 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
 	}
 
 out:
-	mutex_unlock(&memory_tier_lock);
+	mutex_unlock(&default_dram_perf_lock);
 	return rc;
 }
 
 int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
 {
-	if (default_dram_perf_error)
-		return -EIO;
+	int rc = 0;
 
-	if (default_dram_perf_ref_nid == NUMA_NO_NODE)
-		return -ENOENT;
+	mutex_lock(&default_dram_perf_lock);
+	if (default_dram_perf_error) {
+		rc = -EIO;
+		goto out;
+	}
 
 	if (perf->read_latency + perf->write_latency == 0 ||
-	    perf->read_bandwidth + perf->write_bandwidth == 0)
-		return -EINVAL;
+	    perf->read_bandwidth + perf->write_bandwidth == 0) {
+		rc = -EINVAL;
+		goto out;
+	}
 
-	mutex_lock(&memory_tier_lock);
+	if (default_dram_perf_ref_nid == NUMA_NO_NODE) {
+		rc = -ENOENT;
+		goto out;
+	}
 	/*
 	 * The abstract distance of a memory node is in direct proportion to
 	 * its memory latency (read + write) and inversely proportional to its
@@ -745,9 +796,10 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
 		(default_dram_perf.read_latency + default_dram_perf.write_latency) *
 		(default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) /
 		(perf->read_bandwidth + perf->write_bandwidth);
-	mutex_unlock(&memory_tier_lock);
 
-	return 0;
+out:
+	mutex_unlock(&default_dram_perf_lock);
+	return rc;
 }
 EXPORT_SYMBOL_GPL(mt_perf_to_adistance);
 
@@ -858,7 +910,8 @@ static int __init memory_tier_init(void)
 	 * For now we can have 4 faster memory tiers with smaller adistance
 	 * than default DRAM tier.
 	 */
-	default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
+	default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
+									&default_memory_types);
 	if (IS_ERR(default_dram_type))
 		panic("%s() failed to allocate default DRAM tier\n", __func__);
 
@@ -868,6 +921,14 @@ static int __init memory_tier_init(void)
 	 * types assigned.
 	 */
 	for_each_node_state(node, N_MEMORY) {
+		if (!node_state(node, N_CPU))
+			/*
+			 * Defer memory tier initialization on CPUless numa nodes.
+			 * These will be initialized after firmware and devices are
+			 * initialized.
+			 */
+			continue;
+
 		memtier = set_node_memory_tier(node);
 		if (IS_ERR(memtier))
 			/*
-- 
Ho-Ren (Jack) Chuang

Re: [PATCH v10 1/2] memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

[Jonathan Cameron]

On Tue,  2 Apr 2024 00:17:37 +0000
"Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com> wrote:

> Since different memory devices require finding, allocating, and putting
> memory types, these common steps are abstracted in this patch,
> enhancing the scalability and conciseness of the code.
> 
> Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>

Hi,

I know this is a late entry to the discussion but a few comments inline.
(sorry I didn't look earlier!)

All opportunities to improve code complexity and readability as a result
of your factoring out.

Jonathan


> ---
>  drivers/dax/kmem.c           | 20 ++------------------
>  include/linux/memory-tiers.h | 13 +++++++++++++
>  mm/memory-tiers.c            | 32 ++++++++++++++++++++++++++++++++
>  3 files changed, 47 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 42ee360cf4e3..01399e5b53b2 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -55,21 +55,10 @@ static LIST_HEAD(kmem_memory_types);
>  
>  static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
>  {
> -	bool found = false;
>  	struct memory_dev_type *mtype;
>  
>  	mutex_lock(&kmem_memory_type_lock);
could use

	guard(mutex)(&kmem_memory_type_lock);
	return mt_find_alloc_memory_type(adist, &kmem_memory_types);

I'm fine if you ignore this comment though as may be other functions in
here that could take advantage of the cleanup.h stuff in a future patch.

> -	list_for_each_entry(mtype, &kmem_memory_types, list) {
> -		if (mtype->adistance == adist) {
> -			found = true;
> -			break;
> -		}
> -	}
> -	if (!found) {
> -		mtype = alloc_memory_type(adist);
> -		if (!IS_ERR(mtype))
> -			list_add(&mtype->list, &kmem_memory_types);
> -	}
> +	mtype = mt_find_alloc_memory_type(adist, &kmem_memory_types);
>  	mutex_unlock(&kmem_memory_type_lock);
>  
>  	return mtype;
 
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index 69e781900082..a44c03c2ba3a 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -48,6 +48,9 @@ int mt_calc_adistance(int node, int *adist);
>  int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
>  			     const char *source);
>  int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist,
> +							struct list_head *memory_types);

That indent looks unusual.  Align the start of struct with start of int.

> +void mt_put_memory_types(struct list_head *memory_types);
>  #ifdef CONFIG_MIGRATION
>  int next_demotion_node(int node);
>  void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
> @@ -136,5 +139,15 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
>  {
>  	return -EIO;
>  }
> +
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> +{
> +	return NULL;
> +}
> +
> +void mt_put_memory_types(struct list_head *memory_types)
> +{
> +
No blank line needed here. 
> +}
>  #endif	/* CONFIG_NUMA */
>  #endif  /* _LINUX_MEMORY_TIERS_H */
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 0537664620e5..974af10cfdd8 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -623,6 +623,38 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
>  }
>  EXPORT_SYMBOL_GPL(clear_node_memory_type);
>  
> +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)

Breaking this out as a separate function provides opportunity to improve it.
Maybe a follow up patch makes sense given it would no longer be a straight
forward code move.  However in my view it would be simple enough to be obvious
even within this patch.

> +{
> +	bool found = false;
> +	struct memory_dev_type *mtype;
> +
> +	list_for_each_entry(mtype, memory_types, list) {
> +		if (mtype->adistance == adist) {
> +			found = true;

Why not return here?
			return mtype;

> +			break;
> +		}
> +	}
> +	if (!found) {

If returning above, no need for found variable - just do this unconditionally.
+ I suggest you flip logic for simpler to follow code flow.
It's more code but I think a bit easier to read as error handling is
out of the main simple flow.

	mtype = alloc_memory_type(adist);
	if (IS_ERR(mtype))
		return mtype;

	list_add(&mtype->list, memory_types);

	return mtype;

> +		mtype = alloc_memory_type(adist);
> +		if (!IS_ERR(mtype))
> +			list_add(&mtype->list, memory_types);
> +	}
> +
> +	return mtype;
> +}
> +EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
> +
> +void mt_put_memory_types(struct list_head *memory_types)
> +{
> +	struct memory_dev_type *mtype, *mtn;
> +
> +	list_for_each_entry_safe(mtype, mtn, memory_types, list) {
> +		list_del(&mtype->list);
> +		put_memory_type(mtype);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(mt_put_memory_types);
> +
>  static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
>  {
>  	pr_info(

Re: [PATCH v10 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

[Jonathan Cameron]

A few minor comments inline.

> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index a44c03c2ba3a..16769552a338 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -140,12 +140,13 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
>  	return -EIO;
>  }
>  
> -struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> +static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
> +					struct list_head *memory_types)
>  {
>  	return NULL;
>  }
>  
> -void mt_put_memory_types(struct list_head *memory_types)
> +static inline void mt_put_memory_types(struct list_head *memory_types)
>  {
Why in this patch and not previous one?
>  
>  }
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 974af10cfdd8..44fa10980d37 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -36,6 +36,11 @@ struct node_memory_type_map {
>  
>  static DEFINE_MUTEX(memory_tier_lock);
>  static LIST_HEAD(memory_tiers);
> +/*
> + * The list is used to store all memory types that are not created
> + * by a device driver.
> + */
> +static LIST_HEAD(default_memory_types);
>  static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
>  struct memory_dev_type *default_dram_type;
>  
> @@ -108,6 +113,8 @@ static struct demotion_nodes *node_demotion __read_mostly;
>  
>  static BLOCKING_NOTIFIER_HEAD(mt_adistance_algorithms);
>  
> +/* The lock is used to protect `default_dram_perf*` info and nid. */
> +static DEFINE_MUTEX(default_dram_perf_lock);
>  static bool default_dram_perf_error;
>  static struct access_coordinate default_dram_perf;
>  static int default_dram_perf_ref_nid = NUMA_NO_NODE;
> @@ -505,7 +512,8 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
>  static struct memory_tier *set_node_memory_tier(int node)
>  {
>  	struct memory_tier *memtier;
> -	struct memory_dev_type *memtype;
> +	struct memory_dev_type *mtype = default_dram_type;

Does the rename add anything major to the patch?
If not I'd leave it alone to reduce the churn and give
a more readable patch.  If it is worth doing perhaps
a precursor patch?

> +	int adist = MEMTIER_ADISTANCE_DRAM;
>  	pg_data_t *pgdat = NODE_DATA(node);
>  
>  
> @@ -514,11 +522,20 @@ static struct memory_tier *set_node_memory_tier(int node)
>  	if (!node_state(node, N_MEMORY))
>  		return ERR_PTR(-EINVAL);
>  
> -	__init_node_memory_type(node, default_dram_type);
> +	mt_calc_adistance(node, &adist);
> +	if (node_memory_types[node].memtype == NULL) {
> +		mtype = mt_find_alloc_memory_type(adist, &default_memory_types);
> +		if (IS_ERR(mtype)) {
> +			mtype = default_dram_type;
> +			pr_info("Failed to allocate a memory type. Fall back.\n");
> +		}
> +	}
> +
> +	__init_node_memory_type(node, mtype);
>  
> -	memtype = node_memory_types[node].memtype;
> -	node_set(node, memtype->nodes);
> -	memtier = find_create_memory_tier(memtype);
> +	mtype = node_memory_types[node].memtype;
> +	node_set(node, mtype->nodes);
> +	memtier = find_create_memory_tier(mtype);
>  	if (!IS_ERR(memtier))
>  		rcu_assign_pointer(pgdat->memtier, memtier);
>  	return memtier;
> @@ -655,6 +672,33 @@ void mt_put_memory_types(struct list_head *memory_types)
>  }
>  EXPORT_SYMBOL_GPL(mt_put_memory_types);
>  
> +/*
> + * This is invoked via `late_initcall()` to initialize memory tiers for
> + * CPU-less memory nodes after driver initialization, which is
> + * expected to provide `adistance` algorithms.
> + */
> +static int __init memory_tier_late_init(void)
> +{
> +	int nid;
> +
> +	mutex_lock(&memory_tier_lock);
> +	for_each_node_state(nid, N_MEMORY)
> +		if (node_memory_types[nid].memtype == NULL)
> +			/*
> +			 * Some device drivers may have initialized memory tiers
> +			 * between `memory_tier_init()` and `memory_tier_late_init()`,
> +			 * potentially bringing online memory nodes and
> +			 * configuring memory tiers. Exclude them here.
> +			 */

Does the comment refer to this path, or to ones where memtype is set?

> +			set_node_memory_tier(nid);

Given the large comment I would add {} to help with readability.
You could flip the logic to reduce indent
	for_each_node_state(nid, N_MEMORY) {
		if (node_memory_types[nid].memtype)
			continue;
		/*
		 * Some device drivers may have initialized memory tiers
		 * between `memory_tier_init()` and `memory_tier_late_init()`,
		 * potentially bringing online memory nodes and
		 * configuring memory tiers. Exclude them here.
		 */
		set_node_memory_tier(nid);


> +
> +	establish_demotion_targets();
> +	mutex_unlock(&memory_tier_lock);
> +
> +	return 0;
> +}
> +late_initcall(memory_tier_late_init);
> +
>  static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
>  {
>  	pr_info(
> @@ -668,7 +712,7 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
>  {
>  	int rc = 0;
>  
> -	mutex_lock(&memory_tier_lock);
> +	mutex_lock(&default_dram_perf_lock);

As below, this is a classic case where guard() will help readability.

>  	if (default_dram_perf_error) {
>  		rc = -EIO;
>  		goto out;
> @@ -716,23 +760,30 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
>  	}
>  
>  out:
> -	mutex_unlock(&memory_tier_lock);
> +	mutex_unlock(&default_dram_perf_lock);
>  	return rc;
>  }
>  
>  int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
>  {
> -	if (default_dram_perf_error)
> -		return -EIO;
> +	int rc = 0;

Looks like rc is set in all paths that reach where it isused.

>  
> -	if (default_dram_perf_ref_nid == NUMA_NO_NODE)
> -		return -ENOENT;
> +	mutex_lock(&default_dram_perf_lock);

This would benefit quite a lot from
guard(mutex)(&default_dram_perf_lock);
and direct returns throughout.


> +	if (default_dram_perf_error) {
> +		rc = -EIO;
> +		goto out;
> +	}
>  
>  	if (perf->read_latency + perf->write_latency == 0 ||
> -	    perf->read_bandwidth + perf->write_bandwidth == 0)
> -		return -EINVAL;
> +	    perf->read_bandwidth + perf->write_bandwidth == 0) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
>  
> -	mutex_lock(&memory_tier_lock);
> +	if (default_dram_perf_ref_nid == NUMA_NO_NODE) {
> +		rc = -ENOENT;
> +		goto out;
> +	}
>  	/*
>  	 * The abstract distance of a memory node is in direct proportion to
>  	 * its memory latency (read + write) and inversely proportional to its
> @@ -745,9 +796,10 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
>  		(default_dram_perf.read_latency + default_dram_perf.write_latency) *
>  		(default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) /
>  		(perf->read_bandwidth + perf->write_bandwidth);
> -	mutex_unlock(&memory_tier_lock);
>  
> -	return 0;
> +out:
> +	mutex_unlock(&default_dram_perf_lock);
> +	return rc;
>  }
>  EXPORT_SYMBOL_GPL(mt_perf_to_adistance);
>  
> @@ -858,7 +910,8 @@ static int __init memory_tier_init(void)
>  	 * For now we can have 4 faster memory tiers with smaller adistance
>  	 * than default DRAM tier.
>  	 */
> -	default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> +	default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> +									&default_memory_types);

Unusual indenting.  Align with just after (

>  	if (IS_ERR(default_dram_type))
>  		panic("%s() failed to allocate default DRAM tier\n", __func__);
>  
> @@ -868,6 +921,14 @@ static int __init memory_tier_init(void)
>  	 * types assigned.
>  	 */
>  	for_each_node_state(node, N_MEMORY) {
> +		if (!node_state(node, N_CPU))
> +			/*
> +			 * Defer memory tier initialization on CPUless numa nodes.
> +			 * These will be initialized after firmware and devices are

I think this wraps at just over 80 chars.  Seems silly to wrap so tightly and not
quite fit under 80. (this is about 83 chars.

> +			 * initialized.
> +			 */
> +			continue;
> +
>  		memtier = set_node_memory_tier(node);
>  		if (IS_ERR(memtier))
>  			/*

Re: [PATCH v10 1/2] memory tier: dax/kmem: introduce an abstract layer for finding, allocating, and putting memory types

[Ho-Ren (Jack) Chuang]

Hi Jonathan,

Thanks for your feedback. I will fix them (inlined) in the next V11.
No worries, it's never too late!

On Wed, Apr 3, 2024 at 9:52 AM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> On Tue,  2 Apr 2024 00:17:37 +0000
> "Ho-Ren (Jack) Chuang" <horenchuang@bytedance.com> wrote:
>
> > Since different memory devices require finding, allocating, and putting
> > memory types, these common steps are abstracted in this patch,
> > enhancing the scalability and conciseness of the code.
> >
> > Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
> > Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>
> Hi,
>
> I know this is a late entry to the discussion but a few comments inline.
> (sorry I didn't look earlier!)
>
> All opportunities to improve code complexity and readability as a result
> of your factoring out.
>
> Jonathan
>
>
> > ---
> >  drivers/dax/kmem.c           | 20 ++------------------
> >  include/linux/memory-tiers.h | 13 +++++++++++++
> >  mm/memory-tiers.c            | 32 ++++++++++++++++++++++++++++++++
> >  3 files changed, 47 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> > index 42ee360cf4e3..01399e5b53b2 100644
> > --- a/drivers/dax/kmem.c
> > +++ b/drivers/dax/kmem.c
> > @@ -55,21 +55,10 @@ static LIST_HEAD(kmem_memory_types);
> >
> >  static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
> >  {
> > -     bool found = false;
> >       struct memory_dev_type *mtype;
> >
> >       mutex_lock(&kmem_memory_type_lock);
> could use
>
>         guard(mutex)(&kmem_memory_type_lock);
>         return mt_find_alloc_memory_type(adist, &kmem_memory_types);
>

I will change it accordingly.

> I'm fine if you ignore this comment though as may be other functions in
> here that could take advantage of the cleanup.h stuff in a future patch.
>
> > -     list_for_each_entry(mtype, &kmem_memory_types, list) {
> > -             if (mtype->adistance == adist) {
> > -                     found = true;
> > -                     break;
> > -             }
> > -     }
> > -     if (!found) {
> > -             mtype = alloc_memory_type(adist);
> > -             if (!IS_ERR(mtype))
> > -                     list_add(&mtype->list, &kmem_memory_types);
> > -     }
> > +     mtype = mt_find_alloc_memory_type(adist, &kmem_memory_types);
> >       mutex_unlock(&kmem_memory_type_lock);
> >
> >       return mtype;
>
> > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> > index 69e781900082..a44c03c2ba3a 100644
> > --- a/include/linux/memory-tiers.h
> > +++ b/include/linux/memory-tiers.h
> > @@ -48,6 +48,9 @@ int mt_calc_adistance(int node, int *adist);
> >  int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> >                            const char *source);
> >  int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
> > +struct memory_dev_type *mt_find_alloc_memory_type(int adist,
> > +                                                     struct list_head *memory_types);
>
> That indent looks unusual.  Align the start of struct with start of int.
>

I can make this aligned but it will show another warning:
"WARNING: line length of 131 exceeds 100 columns"
Is this ok?

> > +void mt_put_memory_types(struct list_head *memory_types);
> >  #ifdef CONFIG_MIGRATION
> >  int next_demotion_node(int node);
> >  void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
> > @@ -136,5 +139,15 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
> >  {
> >       return -EIO;
> >  }
> > +
> > +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> > +{
> > +     return NULL;
> > +}
> > +
> > +void mt_put_memory_types(struct list_head *memory_types)
> > +{
> > +
> No blank line needed here.

Will fix.

> > +}
> >  #endif       /* CONFIG_NUMA */
> >  #endif  /* _LINUX_MEMORY_TIERS_H */
> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > index 0537664620e5..974af10cfdd8 100644
> > --- a/mm/memory-tiers.c
> > +++ b/mm/memory-tiers.c
> > @@ -623,6 +623,38 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
> >  }
> >  EXPORT_SYMBOL_GPL(clear_node_memory_type);
> >
> > +struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
>
> Breaking this out as a separate function provides opportunity to improve it.
> Maybe a follow up patch makes sense given it would no longer be a straight
> forward code move.  However in my view it would be simple enough to be obvious
> even within this patch.
>

I will just keep this as is for now to minimize the changes aka mistakes.

> > +{
> > +     bool found = false;
> > +     struct memory_dev_type *mtype;
> > +
> > +     list_for_each_entry(mtype, memory_types, list) {
> > +             if (mtype->adistance == adist) {
> > +                     found = true;
>
> Why not return here?
>                         return mtype;
>

Yes, I can return here. I will do that and take care of the ptr
returning at this point.

> > +                     break;
> > +             }
> > +     }
> > +     if (!found) {
>
> If returning above, no need for found variable - just do this unconditionally.
> + I suggest you flip logic for simpler to follow code flow.
> It's more code but I think a bit easier to read as error handling is
> out of the main simple flow.
>
>         mtype = alloc_memory_type(adist);
>         if (IS_ERR(mtype))
>                 return mtype;
>
>         list_add(&mtype->list, memory_types);
>
>         return mtype;
>

Good idea! I will change it accordingly.

> > +             mtype = alloc_memory_type(adist);
> > +             if (!IS_ERR(mtype))
> > +                     list_add(&mtype->list, memory_types);
> > +     }
> > +
> > +     return mtype;
> > +}
> > +EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
> > +
> > +void mt_put_memory_types(struct list_head *memory_types)
> > +{
> > +     struct memory_dev_type *mtype, *mtn;
> > +
> > +     list_for_each_entry_safe(mtype, mtn, memory_types, list) {
> > +             list_del(&mtype->list);
> > +             put_memory_type(mtype);
> > +     }
> > +}
> > +EXPORT_SYMBOL_GPL(mt_put_memory_types);
> > +
> >  static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
> >  {
> >       pr_info(
>


-- 
Best regards,
Ho-Ren (Jack) Chuang
莊賀任

Re: [PATCH v10 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

[Ho-Ren (Jack) Chuang]

Hi Jonathan,

Thank you for your feedback. I will fix them (inlined) in the next V11.

On Wed, Apr 3, 2024 at 10:04 AM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> A few minor comments inline.
>
> > diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> > index a44c03c2ba3a..16769552a338 100644
> > --- a/include/linux/memory-tiers.h
> > +++ b/include/linux/memory-tiers.h
> > @@ -140,12 +140,13 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
> >       return -EIO;
> >  }
> >
> > -struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
> > +static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
> > +                                     struct list_head *memory_types)
> >  {
> >       return NULL;
> >  }
> >
> > -void mt_put_memory_types(struct list_head *memory_types)
> > +static inline void mt_put_memory_types(struct list_head *memory_types)
> >  {
> Why in this patch and not previous one?

I've also noticed this issue. I will fix it in the next V11.

> >
> >  }
> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > index 974af10cfdd8..44fa10980d37 100644
> > --- a/mm/memory-tiers.c
> > +++ b/mm/memory-tiers.c
> > @@ -36,6 +36,11 @@ struct node_memory_type_map {
> >
> >  static DEFINE_MUTEX(memory_tier_lock);
> >  static LIST_HEAD(memory_tiers);
> > +/*
> > + * The list is used to store all memory types that are not created
> > + * by a device driver.
> > + */
> > +static LIST_HEAD(default_memory_types);
> >  static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
> >  struct memory_dev_type *default_dram_type;
> >
> > @@ -108,6 +113,8 @@ static struct demotion_nodes *node_demotion __read_mostly;
> >
> >  static BLOCKING_NOTIFIER_HEAD(mt_adistance_algorithms);
> >
> > +/* The lock is used to protect `default_dram_perf*` info and nid. */
> > +static DEFINE_MUTEX(default_dram_perf_lock);
> >  static bool default_dram_perf_error;
> >  static struct access_coordinate default_dram_perf;
> >  static int default_dram_perf_ref_nid = NUMA_NO_NODE;
> > @@ -505,7 +512,8 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
> >  static struct memory_tier *set_node_memory_tier(int node)
> >  {
> >       struct memory_tier *memtier;
> > -     struct memory_dev_type *memtype;
> > +     struct memory_dev_type *mtype = default_dram_type;
>
> Does the rename add anything major to the patch?
> If not I'd leave it alone to reduce the churn and give
> a more readable patch.  If it is worth doing perhaps
> a precursor patch?
>

Either name works. Keeping it the same name will make the code
easier to follow. I agree! Thanks.

> > +     int adist = MEMTIER_ADISTANCE_DRAM;
> >       pg_data_t *pgdat = NODE_DATA(node);
> >
> >
> > @@ -514,11 +522,20 @@ static struct memory_tier *set_node_memory_tier(int node)
> >       if (!node_state(node, N_MEMORY))
> >               return ERR_PTR(-EINVAL);
> >
> > -     __init_node_memory_type(node, default_dram_type);
> > +     mt_calc_adistance(node, &adist);
> > +     if (node_memory_types[node].memtype == NULL) {
> > +             mtype = mt_find_alloc_memory_type(adist, &default_memory_types);
> > +             if (IS_ERR(mtype)) {
> > +                     mtype = default_dram_type;
> > +                     pr_info("Failed to allocate a memory type. Fall back.\n");
> > +             }
> > +     }
> > +
> > +     __init_node_memory_type(node, mtype);
> >
> > -     memtype = node_memory_types[node].memtype;
> > -     node_set(node, memtype->nodes);
> > -     memtier = find_create_memory_tier(memtype);
> > +     mtype = node_memory_types[node].memtype;
> > +     node_set(node, mtype->nodes);
> > +     memtier = find_create_memory_tier(mtype);
> >       if (!IS_ERR(memtier))
> >               rcu_assign_pointer(pgdat->memtier, memtier);
> >       return memtier;
> > @@ -655,6 +672,33 @@ void mt_put_memory_types(struct list_head *memory_types)
> >  }
> >  EXPORT_SYMBOL_GPL(mt_put_memory_types);
> >
> > +/*
> > + * This is invoked via `late_initcall()` to initialize memory tiers for
> > + * CPU-less memory nodes after driver initialization, which is
> > + * expected to provide `adistance` algorithms.
> > + */
> > +static int __init memory_tier_late_init(void)
> > +{
> > +     int nid;
> > +
> > +     mutex_lock(&memory_tier_lock);
> > +     for_each_node_state(nid, N_MEMORY)
> > +             if (node_memory_types[nid].memtype == NULL)
> > +                     /*
> > +                      * Some device drivers may have initialized memory tiers
> > +                      * between `memory_tier_init()` and `memory_tier_late_init()`,
> > +                      * potentially bringing online memory nodes and
> > +                      * configuring memory tiers. Exclude them here.
> > +                      */
>
> Does the comment refer to this path, or to ones where memtype is set?
>

Yes, the comment is for explaining why the if condition is used.

> > +                     set_node_memory_tier(nid);
>
> Given the large comment I would add {} to help with readability.
> You could flip the logic to reduce indent
>         for_each_node_state(nid, N_MEMORY) {
>                 if (node_memory_types[nid].memtype)
>                         continue;
>                 /*
>                  * Some device drivers may have initialized memory tiers
>                  * between `memory_tier_init()` and `memory_tier_late_init()`,
>                  * potentially bringing online memory nodes and
>                  * configuring memory tiers. Exclude them here.
>                  */
>                 set_node_memory_tier(nid);
>
>

I will change it accordingly.

> > +
> > +     establish_demotion_targets();
> > +     mutex_unlock(&memory_tier_lock);
> > +
> > +     return 0;
> > +}
> > +late_initcall(memory_tier_late_init);
> > +
> >  static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
> >  {
> >       pr_info(
> > @@ -668,7 +712,7 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> >  {
> >       int rc = 0;
> >
> > -     mutex_lock(&memory_tier_lock);
> > +     mutex_lock(&default_dram_perf_lock);
>
> As below, this is a classic case where guard() will help readability.
>

I will change it accordingly.

> >       if (default_dram_perf_error) {
> >               rc = -EIO;
> >               goto out;
> > @@ -716,23 +760,30 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
> >       }
> >
> >  out:
> > -     mutex_unlock(&memory_tier_lock);
> > +     mutex_unlock(&default_dram_perf_lock);
> >       return rc;
> >  }
> >
> >  int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
> >  {
> > -     if (default_dram_perf_error)
> > -             return -EIO;
> > +     int rc = 0;
>
> Looks like rc is set in all paths that reach where it issued.
>

Using guard(mutex), I will no longer need `int rc`.
Replace `rc =` with `return XXX`.

> >
> > -     if (default_dram_perf_ref_nid == NUMA_NO_NODE)
> > -             return -ENOENT;
> > +     mutex_lock(&default_dram_perf_lock);
>
> This would benefit quite a lot from
> guard(mutex)(&default_dram_perf_lock);
> and direct returns throughout.
>

Got it. I will change it accordingly.

>
> > +     if (default_dram_perf_error) {
> > +             rc = -EIO;
> > +             goto out;
> > +     }
> >
> >       if (perf->read_latency + perf->write_latency == 0 ||
> > -         perf->read_bandwidth + perf->write_bandwidth == 0)
> > -             return -EINVAL;
> > +         perf->read_bandwidth + perf->write_bandwidth == 0) {
> > +             rc = -EINVAL;
> > +             goto out;
> > +     }
> >
> > -     mutex_lock(&memory_tier_lock);
> > +     if (default_dram_perf_ref_nid == NUMA_NO_NODE) {
> > +             rc = -ENOENT;
> > +             goto out;
> > +     }
> >       /*
> >        * The abstract distance of a memory node is in direct proportion to
> >        * its memory latency (read + write) and inversely proportional to its
> > @@ -745,9 +796,10 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
> >               (default_dram_perf.read_latency + default_dram_perf.write_latency) *
> >               (default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) /
> >               (perf->read_bandwidth + perf->write_bandwidth);
> > -     mutex_unlock(&memory_tier_lock);
> >
> > -     return 0;
> > +out:
> > +     mutex_unlock(&default_dram_perf_lock);
> > +     return rc;
> >  }
> >  EXPORT_SYMBOL_GPL(mt_perf_to_adistance);
> >
> > @@ -858,7 +910,8 @@ static int __init memory_tier_init(void)
> >        * For now we can have 4 faster memory tiers with smaller adistance
> >        * than default DRAM tier.
> >        */
> > -     default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> > +     default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> > +                                                                     &default_memory_types);
>
> Unusual indenting.  Align with just after (
>

Aligning with "(" will exceed 100 columns. Would that be acceptable?

> >       if (IS_ERR(default_dram_type))
> >               panic("%s() failed to allocate default DRAM tier\n", __func__);
> >
> > @@ -868,6 +921,14 @@ static int __init memory_tier_init(void)
> >        * types assigned.
> >        */
> >       for_each_node_state(node, N_MEMORY) {
> > +             if (!node_state(node, N_CPU))
> > +                     /*
> > +                      * Defer memory tier initialization on CPUless numa nodes.
> > +                      * These will be initialized after firmware and devices are
>
> I think this wraps at just over 80 chars.  Seems silly to wrap so tightly and not
> quite fit under 80. (this is about 83 chars.
>

I can fix this.
I have a question. From my patch, this is <80 chars. However,
in an email, this is >80 chars. Does that mean we need to
count the number of chars in an email, not in a patch? Or if I
missed something? like vim configuration or?

> > +                      * initialized.
> > +                      */
> > +                     continue;
> > +
> >               memtier = set_node_memory_tier(node);
> >               if (IS_ERR(memtier))
> >                       /*
>


-- 
Best regards,
Ho-Ren (Jack) Chuang
莊賀任

Re: [PATCH v10 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

[Jonathan Cameron]

<snip>

> > > @@ -858,7 +910,8 @@ static int __init memory_tier_init(void)
> > >        * For now we can have 4 faster memory tiers with smaller adistance
> > >        * than default DRAM tier.
> > >        */
> > > -     default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> > > +     default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> > > +                                                                     &default_memory_types);  
> >
> > Unusual indenting.  Align with just after (
> >  
> 
> Aligning with "(" will exceed 100 columns. Would that be acceptable?
I think we are talking cross purposes.

	default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
						      &default_memory_types);  

Is what I was suggesting.

> 
> > >       if (IS_ERR(default_dram_type))
> > >               panic("%s() failed to allocate default DRAM tier\n", __func__);
> > >
> > > @@ -868,6 +921,14 @@ static int __init memory_tier_init(void)
> > >        * types assigned.
> > >        */
> > >       for_each_node_state(node, N_MEMORY) {
> > > +             if (!node_state(node, N_CPU))
> > > +                     /*
> > > +                      * Defer memory tier initialization on CPUless numa nodes.
> > > +                      * These will be initialized after firmware and devices are  
> >
> > I think this wraps at just over 80 chars.  Seems silly to wrap so tightly and not
> > quite fit under 80. (this is about 83 chars.
> >  
> 
> I can fix this.
> I have a question. From my patch, this is <80 chars. However,
> in an email, this is >80 chars. Does that mean we need to
> count the number of chars in an email, not in a patch? Or if I
> missed something? like vim configuration or?

3 tabs + 1 space + the text from * (58)
= 24 + 1 + 58 = 83

Advantage of using claws email for kernel stuff is it has a nice per character
ruler at the top of the window.

I wonder if you have a different tab indent size?  The kernel uses 8
characters.  It might explain the few other odd indents if perhaps
you have it at 4 in your editor?

https://www.kernel.org/doc/html/v4.10/process/coding-style.html

Jonathan

> 
> > > +                      * initialized.
> > > +                      */
> > > +                     continue;
> > > +
> > >               memtier = set_node_memory_tier(node);
> > >               if (IS_ERR(memtier))
> > >                       /*  
> >  
> 
> 

Re: [External] Re: [PATCH v10 2/2] memory tier: create CPUless memory tiers after obtaining HMAT info

[Ho-Ren (Jack) Chuang]

Hi Jonathan,

Thank you! I will fix them and send a V11 soon.

On Thu, Apr 4, 2024 at 6:37 AM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> <snip>
>
> > > > @@ -858,7 +910,8 @@ static int __init memory_tier_init(void)
> > > >        * For now we can have 4 faster memory tiers with smaller adistance
> > > >        * than default DRAM tier.
> > > >        */
> > > > -     default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> > > > +     default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> > > > +                                                                     &default_memory_types);
> > >
> > > Unusual indenting.  Align with just after (
> > >
> >
> > Aligning with "(" will exceed 100 columns. Would that be acceptable?
> I think we are talking cross purposes.
>
>         default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
>                                                       &default_memory_types);
>
> Is what I was suggesting.
>

Oh, now I see. Thanks!

> >
> > > >       if (IS_ERR(default_dram_type))
> > > >               panic("%s() failed to allocate default DRAM tier\n", __func__);
> > > >
> > > > @@ -868,6 +921,14 @@ static int __init memory_tier_init(void)
> > > >        * types assigned.
> > > >        */
> > > >       for_each_node_state(node, N_MEMORY) {
> > > > +             if (!node_state(node, N_CPU))
> > > > +                     /*
> > > > +                      * Defer memory tier initialization on CPUless numa nodes.
> > > > +                      * These will be initialized after firmware and devices are
> > >
> > > I think this wraps at just over 80 chars.  Seems silly to wrap so tightly and not
> > > quite fit under 80. (this is about 83 chars.
> > >
> >
> > I can fix this.
> > I have a question. From my patch, this is <80 chars. However,
> > in an email, this is >80 chars. Does that mean we need to
> > count the number of chars in an email, not in a patch? Or if I
> > missed something? like vim configuration or?
>
> 3 tabs + 1 space + the text from * (58)
> = 24 + 1 + 58 = 83
>
> Advantage of using claws email for kernel stuff is it has a nice per character
> ruler at the top of the window.
>
> I wonder if you have a different tab indent size?  The kernel uses 8
> characters.  It might explain the few other odd indents if perhaps
> you have it at 4 in your editor?
>
> https://www.kernel.org/doc/html/v4.10/process/coding-style.html
>

Got it. I was using tab=4. I will change to 8. Thanks!

> Jonathan
>
> >
> > > > +                      * initialized.
> > > > +                      */
> > > > +                     continue;
> > > > +
> > > >               memtier = set_node_memory_tier(node);
> > > >               if (IS_ERR(memtier))
> > > >                       /*
> > >
> >
> >
>


-- 
Best regards,
Ho-Ren (Jack) Chuang
莊賀任